Data Room Setup

1. On the Cornell Chopper box, turn on the chopping secondary power and look for the drive and response signals on the oscilloscope. Set the amplitude to the desired value with the Gain knob, and rotate the chop to the desired direction using the toggle switch on the Caltech f/70 chopping secondary control panel. Because these functions are manually controlled, the SC-10 computer has no knowledge of their values. Write them down if they are important to you!

2. Set the telescope focus to about 62.00 mm, if a better value has not been determined (set with the hand paddle, make sure focus is switched on at the N.A.'s desk).

3. Log onto GRB as scuser. A Terminal window should automatically open. If one doesn't open, right-click on the Desktop, select "Tools", then select "Terminal".

4. Check the available disk space with the df -k command. The 31 Gig /scr1 partition is likely where you will want to write your data. But you are free to use the 8 Gig /scr or the 3.5 Gig /sc2 partitions. You may need to clear some space; get help if you're not sure what to do.

5. In the Terminal Window, type sc10. The SC-10 programs will load.

6. Enter the Observers' names into the Initialization menu upper line, and the directory name for the data files on the lower line. The default name is "daycrew"; the default directory is "/scr/xyz". Note that the /scr1 disk is a 31 Gigabyte disk. Press Return to enter the text and check the results. We usually name the directory to reflect the UT date of the observations. For example, if the UT date is September 25, 1994, enter sep25 on the line.

7. Select the Use Guider checkbox if Sam's terminal cable is connected to serial port B and you want to run MIRELLA in an XTerm window.

8. Press the Accept button and answer the confirming box that will pop up if you haven't pressed Return. The SC-10 Data Acquistion program will appear shortly. The Display program should have already loaded and be visible at the bottom of the screen.

9. Move the mouse cursor to the Display window. Some of the buttons in the window should turn green as the color map is changed. Press CTRL-L2 to lock the color map. A reminder to do this is printed in the Console window every time the Display program is run.

10. Press the PC Connection button (upper left corner of the Acquistion program window), and press the Establish Connection button in the pop-up menu to establish the ethernet connection to the PC. If the connection fails, there may be a problem in the cabling, or the PC may not be ``listening'' for the connection.

    If the connection needs to be broken, then reestablished, you may get a Syserr response and an error message in the console window when you press the connect button, indicating that the address that GRB is attempting to establish is already in use by the PC. Just press the Establish Connection button again and the system will try to connect using a different address. After several disconnections and reconnections, the system may refuse to connect after several tries. In this case, rebooting the PC with the Reboot button in the PC Connection menu should reset the network software and allow a connection.

11. Try a simple command like moving the filter or resetting the integration time to make sure the network connection is working.

12. Check the noise level of the detector. This is listed as SD on the display (Standard Deviation). Set the filter to the block position, the Instrument Mode to Camera, and open the Integration Parameters menu (under the System Parameters button). Check that the Phase is set to about 0 degrees, choose the 64x 64 pixel, sub-buffer chopping ROM table with 8 frames per chop, and set the chop frequency to about 1 Hz. This should give a Frame Rate of about 8 Hz and a Group Rate of 12.4 kHz. Set the Cont. Acq. Integration Time to about 2 sec.

13. Set the Gain to 80 and the Bandwidth to 50. Turn on Cont. Acq. Mode, show Buf0 in the SCDISP window, select units of mV, and set the mouse to photometry mode. The average signal should be a few hundred mV with the frame rate specified above; this is mostly preamplifier offset. Change the display to Show Diff (you will now see Buf0 - Buf1), the units to e- , and measure the noise. In e- units, the noise is normalized to 1 frame, unlike the other modes where it represents the noise of the average of many frames summed by the coadder. The noise per frame should be about 350 e- with the detector dark. If it is higher make sure the gain and bandwidth are set to the values given above. If the gain is too low then A/D bit noise will dominate, and if the bandwidth is too high then noise from sources other than the detector may dominate.

14. Choose the 64x64, 32 Frames per Chop ROM table and a chop frequency of about 5 Hz. The group rate should now be about 240 kHz. Set the Gain to 10. In general, the gain should be kept as low as possible, and the detector run as slowly as possible to fill up the wells. A gain of 10 is usually preferred for camera and lo-res modes, but a gain of 40 may be necessary for hi-res mode where the detector output will be very low. Set the Bandwidth to 3000. The Bandwidth should always be set to the smallest value that is at least 5 times the group rate. Make sure the other Integration Parameters are set to desired values. Typically we set the Cont. Acq. Integration Time to about 2 sec and the Nod Delay to about 5000 msec. The Nodding and Chopping buttons should both be on for beam-switched scans. Note, however, that setting the Chopping button simply tells the software to expect chopped data, it does not actually turn the chopper on and off.

15. Have the telescope operator open the dome and mirror covers.

16. Open the secondary lid using the switch on the Caltech panel, located at the very bottom of the electronics rack. The LED should change from Green (closed) to Red (open) and you should hear a loud tone when the lid reaches the open position. Note that the lid covers the top of the secondary, eliminating the sky at short wavelengths (< 2 microns) since the sky is brighter up to 2 microns. At wavelengths greater than 2 microns, the lid is brighter than the sky, so it should be removed.

17. Select the 8.8 um filter and the Open slit. turn on the Cont. Acq. mode again, and show Buf0. Most of the array should be brightly illuminated. Looking up at the Zenith with this filter, there should be several thousand millivolts of signal. If the detector is saturated (about 18,000 mV, with all pixels having exactly the same value), check to be sure that the optical path is clear, the filter is correct, and the detector frame rate is correct. If the array is dark, the GSM may not be set up properly. A smaller ROM table or lower bias voltage may be required if the weather is so warm that the detector keeps saturating.

18. Open the GSM menu, select the Shift all Modes button, and use the pixel motion commands to position the image where you want it. Be aware that the image lies at a slightly different spot for each filter because the filter substrates are slightly wedged. The best position will depend on whether you just want to use one filter, or step through the entire set.